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Old 16th October 2011, 05:51 PM   #71
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by Tony View Post
of course you can....
does that mean you can assume a high Tesla compatible steel. Then check that assumption by measuring the primary loss.
If the guess was wrong then add more turns.Is that an acceptable procedure if one does not know what steel has been used for the core nor does one know the maximum Tesla suitable for that core?
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Old 16th October 2011, 07:13 PM   #72
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Is that an acceptable procedure if one does not know what steel has been used for the core nor does one know the maximum Tesla suitable for that core?
When laminates are 0,35 mm you probably deal with good quality (corn oriented) M6; stay under 1,5T.
When laminates are 0,5 mm it is definetely one of the lower grades; stay under 1T.
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Old 16th October 2011, 11:03 PM   #73
AndrewT is offline AndrewT  Scotland
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How does one measure the thickness of the lamination in a toroid when it is completely hidden from view?

How can one be sure that 1T and 1.5T are the best performance targets for the two thicknesses that you quote?

What if the thickness is other than the two you quote.

I am trying to find a method that is fairly simple that can confirm that the correct number of turns have been wound onto the core.
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Old 16th October 2011, 11:20 PM   #74
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Quote:
How does one measure the thickness of the lamination in a toroid when it is completely hidden from view?
By removing the copper and insulation

Quote:
How can one be sure that 1T and 1.5T are the best performance targets for the two thicknesses that you quote?
Not "the best performance targets", but mere guidelines based on properties of the materials.

Quote:
What if the thickness is other than the two you quote.
Let us know when it is different.

Quote:
I am trying to find a method that is fairly simple that can confirm that the correct number of turns have been wound onto the core.
My calculations are based on sheets for the specific materials provided by the manufacturer, in my case specifically for c-cores.
Maybe you can find data for toroidal cores as well searching the net.
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Old 16th October 2011, 11:24 PM   #75
AndrewT is offline AndrewT  Scotland
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Originally Posted by AndrewT View Post
If one winds on the primary, can one test the primary current vs supply voltage to check that there are sufficient turns on the transformer to avoid the knee showing the onset of core saturation?
Quote:
Originally Posted by Tony View Post
of course you can....in my designs i go for low magnetizing currents, that is why i go for low teslas....
I am reluctantly repeating my question and the first reponse to it.

Your specific cases do not get me any closer to an answer.
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Old 17th October 2011, 12:01 AM   #76
AJT is offline AJT  Philippines
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Hi AndrewT,

Chapter5 of RDH4 gives a lot of answers........you can read it and find out....

designing transformers, you will find that calculating the primary turns, you may get a figure say 200, but when computing for the number of turns per layer, and number of layers, you will realize that you actually end up with say 220, or even 180......what i a m saying is that it takes practice to know these things....

pieter t said it eloquently,
Quote:
Not "the best performance targets", but mere guidelines based on properties of the materials
again, pieter t put it as
Quote:
When laminates are 0,35 mm you probably deal with good quality (corn oriented) M6; stay under 1,5T.
When laminates are 0,5 mm it is definetely one of the lower grades; stay under 1T.
i tend to go lower than these guidelines, these are choices designers make, we can not teach you how to make those choices, you have to find it out on your own....

making diy traffos, i am not constrained by cost.....

it all boils down to designing traffos that you are happy about the losses therein....
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Old 17th October 2011, 12:03 AM   #77
AJT is offline AJT  Philippines
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Originally Posted by pieter t View Post
0.1 mm is well known material; meant for 400 Hz applications (power supply for planes for instance where weight matters).
Not well suited for a 50/60 Hz power supply transformer because the max T at those frequencies will be very low.
However you might use it for a very good output transformer.
i would surely want to get my hands on these materials....
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Old 17th October 2011, 12:14 AM   #78
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Andrew,

Look at Transformers for some pretty good information.

Standard toroids are generally wound with 1,6-1,8T, using 0,35mm corn oriented cores.
When you know the number of primary turns, doubling that number would halve B max, or whatever you want in between. This is a linear function.
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Old 17th October 2011, 10:35 AM   #79
AndrewT is offline AndrewT  Scotland
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Tony, thanks. I have read a few of the previous references you have provided.
I do take the point that one calculates or estimates the primary turns.
That I accept is not the end of the primary design.

I am looking for what comes next.
Checking that the primary turns has been correctly estimated. That is where your experience comes in could it be that the required turns needs to be adjusted +-10%?
I and all the other Members trying to learn from you need to be able to replace "your experience" with a method that shows we have it right or shows how much we have estimated wrongly.
That's why I ask for a measurment/test method so that we don't stop after the first guess and know what direction to adjust our guess to get the performance we are trying to design in.

Peter,
taking a blanket statement of 0.35mm use <1.5T, or 0.5mm use <1.0T, or toroid between 1.6T & 1.8T, gets me no where to wards knowing I have got the primary turns correct.
Read my reply to Peter and maybe you will better understand why and what I am asking.

ps, I read Tommy's paper, or an earlier version of it, about 10years ago.
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Last edited by AndrewT; 17th October 2011 at 10:40 AM.
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Old 17th October 2011, 10:48 AM   #80
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Peter,
taking a blanket statement of 0.35mm use <1.5T, or 0.5mm use <1.0T, or toroid between 1.6T & 1.8T, gets me no where to wards knowing I have got the primary turns correct.
Read my reply to Peter and maybe you will better understand why and what I am asking.
It is not so difficult.
Important is to know:
1. what core material you have there;
2. count the number of primary windings;
3. primary (line) voltage.
Then you can easily calculate B max, and change it when you want.
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